The present invention relates to an intake valve device for preventing adhesion of deposits.
In poppet valves in engines of automobiles and ships, especially, in intake valves which has relatively low heat load, if high boiling point organic substances in lubricating oil leaked from a gap between a valve guide and a valve stem adhere to a valve head and adjacent area, they will be carbonized at of 200.degree. to 300.degree. C. of the intake valve, gradually aggregated and developed, thereby forming sludges or bulk of deposits. In the deposits, corrosion ingredients may be contained, which causes corrosion in the valve head and adjacent area.
To overcome the disadvantages on the surface of the valve head and adjacent area, an intake valve is suggested as mentioned Japanese Patent Laid-Open Pub. No. 6-235308, wherein a coating layer which has oxidation catalytic function is formed on the valve head and adjacent area, thereby preventing high boiling point organic substances from adhering on the valve head and adjacent area owing to oxidation catalytic reaction thereof. However, in the intake valve in this publication, an engine runs for a long time at low load and speed, so that the surface of catalyst is partially covered with high boiling point organic substances in the lubricating oil owing to oil-down until the intake valve becomes reaction temperature of the catalyst, and the catalyst is blocked against air or oxygen. Thus, oxidization catalytic reaction may not be achieved enough.